Mukesh Ambani 18th richest; Slim still the fattest cat

Indian business leader Mukesh Ambani is the 18th richest man in the world, with a personal fortune of $24.7 billion in 2012, according to the Bloomberg Billionaires Index, a daily ranking of the world's 100 wealthiest individuals.

Mexican telecommunications magnate Carlos Slim remained the world's richest person of the year just past, with a personal fortune of more than $70 billion.

Ambani, 55, is the chairman and managing director of Reliance Industries, a conglomerate with its fingers in many pies. He continues to retain his position as the richest Indian for the sixth year in a row.

On the Bloomberg index, he is up a notch from 19th position in 2011; his personal wealth is up from $21 billion to $24.7 billion in the world.

Microsoft founder Bill Gates and the founder of fashion retailer Zara, Amancio Ortega, rounded out the top three spots, with wealth estimated just over and just under $60 billion respectively.

Amid a continuing global business turndown, the world's top 100 billionaires got even richer in 2012, with their total wealth rising by around 15 per cent to $1.81 trillion.